Hydraulic pump driven by an internal combustion engine

ABSTRACT

A hydraulic pump driven by an internal combustion engine is an externally pressurized radial piston pump, which is internally driven by an eccentric. The hydraulic pump is integrated within the cylinder head of an internal combustion engine.

This application is the U.S. national-phase application of PCTInternational Application No. PCT/EP93/01175.

This application is the U.S. national-phase application of PCTInternational Application No. PCT/EP93/01175.

BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic pump driven by an internalcombustion engine. More particularly, the present invention relates to ahydraulic unit or system including a hydraulic pump driven by a camshaftof an internal combustion engine for providing pressure fluid toengine-compartment consumers in automotive vehicles.

A pump of this type is disclosed in German Patent Publication numberDE-OS 40 33 105. According to the system disclosed by this reference aninternally pressurized radial piston pump is flanged to the enginehousing and has an air-flow sensor flap between the pump housing and theengine housing. The phrase "internally pressurized" means that thepressurization of the fluid occurs radially inward relative to thepiston. The airflow sensor flap is provided with a central opening,through which a clutch extends that interconnects the pump motor and thedrive shaft of the engine.

Undesirably, this known system requires a large number of componentparts and the pump of this system necessitates a relatively largemounting space. In particular, in up-to-date automotive vehicles, it isdesirable to reduce the dimensions of the units which are accommodatedin the engine compartment to the greatest possible extent.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a generichydraulic pump which requires only a reduced number of component parts,which affords greater ease of assembly and, in addition, necessitatesless mounting space. This object is achieved by providing a hydraulicpump which is an externally pressurized and internally driven radialpiston pump, having at least one pump piston, and which is integratedinto the cylinder head of the internal combustion engine. The phrase"externally pressurized" means that the pressurization of the fluidoccurs radially outward relative to the pump piston. Similarly, thephrase "internally driven" means that the mechanism which drives thepiston is radially inward relative to the pump piston.

Designing a hydraulic pump as an internally driven radial piston pump,driven by an eccentric, for example, is inexpensive because a reducednumber of component parts is needed, thereby diminishing the assemblingeffort. In addition, it is possible to use low-cost pump elements ofexisting series. Further, an externally pressurized pump may have shortdimensions in the axial direction. The radial extension of such a pumpis dictated by the number and size of the pump pistons used, both ofwhich can be adapted to the demanded pressure fluid requirement. Theattachment of the piston may be conformed to the space requirements, inparticular, in case only one piston is used.

The system of the present invention permits a particularly shortconstruction of the pump. Integrating the pump into the cylinder head ofthe internal combustion engine is an economy in overall size as comparedto a flanged component part. More specifically, the pump is actuallyformed within the cylinder head, for example, by being disposed withinthe axial length of the cylinder head wall of the cylinder head. Thecylinder head may be expediently provided with openings and chambers,which can be prepared for the incorporation of the pump elements, inonly a few additional machining steps. These machining steps essentiallyimply the provision of bores. The operating shaft serving to drive thepump may be any desired spacer shaft of the engine, for example a shaftof the distributor drive, or a shaft of the lubrication pump drive.

According to a preferred embodiment of the present invention, thecamshaft, or one of the camshafts of the internal combustion engine, isused as the drive shaft. An eccentric or a cam, possibly a valve cam,which is incorporated in the camshaft may serve as a pump drive. Sincethe eccentric or the cam serving as the pump drive may be arranged onthe camshaft at any desired location, it is possible to arrange the pumpat any chosen location, such as at an especially suitable positionrelative to the cylinder head.

According to another embodiment of the present invention, a free end ofa camshaft of the internal combustion engine is provided as the pumpdrive. This free end of the camshaft must be extended appropriately andconfigured to drive the pump.

According to another embodiment of the present invention, the end of thecamshaft is provided with an eccentric on which a ball race is rotatablymounted. The pump piston or pistons take support on the ball race. Theeccentric may be provided by the camshaft having an eccentricallyarranged section. It may be less expensive to design the camshaft endsuch that an eccentric component can be fitted thereon. Thus, theboundary surface between the camshaft end and the eccentric may bedesigned as a toothed truncated cone-shaped surface, for example, whichpermits ease of assembly and precludes relative rotation between thecamshaft and the eccentric. Of course, when the camshaft is supportedappropriately, the eccentric surface may also be machined therein. Therotatable ball race may be seated on the eccentric in a friction bearingor a needle bearing.

The mounting support of the camshaft in the cylinder head according toan aspect of the invention is able to absorb forces which are exerted bythe pump on the camshaft. This prevents impairment of the functioning ofthe pump.

Still shorter overall dimensions of the pump and, hence, of the housingof the internal combustion engine, can be achieved if, according toanother aspect of the invention, bearings of the camshaft are providedin the cylinder shaft which are able to absorb the forces exerted by thepump on the camshaft. In this event, the area of the cylinder headbetween the engine compartment and the pump chamber may have a very thindesign.

According to a preferred embodiment of the hydraulic pump according tothe present invention which lends itself to particular ease ofmanufacture, an opening leading to the cylinder head is provided in thecylinder head wall, through which the free end of the camshaft extends.This opening is succeeded by a hollow space accommodating the ball raceand the eccentric, and the cylinder head wall contains at least onecylinder bore in which each piston is guided. Also, the suction channeland the pressure channel extend through the cylinder head wall.

According to another embodiment of the present invention, the pumpchamber is closed towards the outside by a cover, which permits ease ofassembly of the pump.

Still another embodiment of the present invention incorporates part ofthe suction channel of the pump in the cover and provides restrictors inthe cover. This embodiment is favorable in that the cover may bemachined independently of the cylinder head and delivered inprefabricated condition for the assembly. The restrictor permitsoperation of the pump with choked suction, which means that no more thanthe maximum required fluid volume is supplied, even if the camshaft runsat a higher speed than necessary for the maximum fluid flow. Thus,suction throttling economizes energy.

According to another preferred embodiment of the present invention, thecover in the fringe area is round in shape and is furnished with acircumferential annular groove which forms one boundary surface of asuction channel, while the other boundary surface is formed by thecylinder head. The bores leading from the circumferential annular grooveto the side of the cover close to the cylinder head are the restrictors,through which pump pistons may aspirate the pressure fluid. The recessprovided in the middle of the cover may serve to accommodate attachmentmeans to attach the eccentric of a camshaft.

According to another embodiment of the present invention, theintermediate reservoir is incorporated in the cylinder head wall. Theintermediate reservoir may be produced by providing a hole extendingtowards the annular channel of the cover in a simple manner.

According to another embodiment of the present invention, thelubricating oil of the internal combustion engine, which is deliveredinto the intermediate reservoir by a lubricating oil pump, is used asthe pressure fluid. Advantageously, leakage from the pump to the enginecompartment is tolerable, so that there is no need for additionalpressure fluid, and fluid return is permitted from the consumer orconsumers into the oil pan of the internal combustion engine.

The hydraulic pump according to the present invention is appropriate forsupplying pressure fluid to consumers in automotive vehicles. Thehydraulic pump of the present invention is particularly appropriate forsupplying pressure fluid to either a camshaft adjusting device, anautomatic clutch, a differential lock, a slip control system or a powersteering system, or any combination of such consumers at the same time.These consumers are arranged close to the internal combustion engine andmust be furnished with pressure fluid.

The pump according to the present invention is particularly well suitedfor supplying a camshaft adjusting device with pressure fluid, since thecamshaft adjusting device also may be attached directly to the cylinderhead of the internal combustion engine. Various designs are possible andparticularly short pressure fluid conduits are required when thecamshaft adjusting device and the hydraulic pump are arranged at theinlet camshaft and/or outlet camshaft on the same side of the engineblock. Depending on the respective engine construction, the conduits maybe cast-in or drilled channels, or part of the conduits may be providedas screwed pipes.

It is possible to adjust several camshafts irrespective of one anotherwhen the camshaft adjusting device and the hydraulic pump are attachedat the opposed ends of a camshaft. If desired, further camshafts of theinternal combustion engine may be equipped with camshaft adjustingdevices. Thus, it is possible to adjust also the camshafts which drivethe hydraulic pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention and their operation can beseen in the drawings, in which:

FIG. 1 is a schematic diagram of a hydraulic unit, including a hydraulicpump according to the present invention, and

FIG. 2 is a partial cross-section of the hydraulic pump according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a portion of the lubrication system of an internalcombustion engine including an oil pan 1, a lubrication pressure pump 2,a filter 3 and a lubrication pressure line 4. Branching off from thelubrication pressure line 4 is a supply line 5 containing a restrictor 6which terminates into an intermediate reservoir 7 with an overflow tank8. The intermediate reservoir 7 is part of a hydraulic unit whichcomprises a suction-controlled hydraulic pump 9, a pressure-limitingvalve 10, an electromagnetically operable control valve 11 and anoperating cylinder 12. The operating cylinder 12 may serve to operate aconsumer 19, such as a variable camshaft adjusting device. Consumer 19may represent other consumers, such as an automatic clutch, adifferential lock, a slip control system, a power steering system, orcombinations thereof.

The suction side of the hydraulic pump 9 is connected to theintermediate reservoir 7 through a restrictor 13 for the purpose ofsuction control of the delivery rate. The pressure side of the hydraulicpump 9 is in direct connection with the piston rod side of the operatingcylinder 12. To perform adjusting movements, the side of the operatingcylinder 12 remote from the piston rod is connected, by way of thecontrol valve 11, either with the pressure side of the hydraulic pump 9or, through a return line 14, with the oil pan 1. In an intermediateposition, the control valve 11 is closed, and the piston of theoperating cylinder 12 is stopped in a position which it reaches due tothe surrounding pressurization. Also, a return line 15 leads from thepressure-limiting valve 10 to the oil pan 1.

Variations in the operating pressure of the lubrication system of aninternal combustion engine are substantial due to the rotational speedof the engine and the operating temperature. Nonetheless, the hydraulicunit of the present invention may expediently use the lubrication systemof an internal combustion engine in spite of such variations in theoperating pressure in order to deliver operating media to the hydraulicpump 9 driven by the internal combustion engine. The unpressurizedintermediate reservoir permits suction pressure control of the hydraulicpump 9 so that the delivery rate of the hydraulic pump 9 can easily belimited to an appropriate maximum value, while small losses areinvolved, despite major rotational speed variations of the pump drive.

FIG. 2 shows an embodiment of the hydraulic pump 9 (shown as pumpelement 20 in FIG. 2) according to the present invention. On the leftside (as shown in FIG. 2) is the cylinder head 27, the right-handboundary portion of which is a cylinder head wall 17. An opening 18 iscontained in the cylinder head wall 17, in which the camshaft 33 (havinga cam 34) is seated by way of a bearing 22. Fitted to the right-hand endof the camshaft 33 is a conical section 39, which is of toothed designand on which an eccentric 26 is seated which is toothed as well. Thetoothed engagement precludes relative rotation between the eccentric 26and the conical section 39 of the camshaft 33. The eccentric 26 isprotected against axial displacement by means of a set-screw 40 fittedto the end of the camshaft 33. A ball race 25 is rotatably mounted onthe eccentric 26.

In the cylinder head wall 17, the intermediate reservoir 7 is arranged,into which the supply line 5 from the lubrication pressure pump 2terminates and which is provided with an overflow tank 8 (not shown inFIG. 2). Channel 41, which extends from the intermediate reservoir 7,forms part of the suction channel 28 which is continued in acircumferential annular groove 32 in the cover 37. Cover 37 confines thehollow space 16, formed in the cylinder head wall 18, towards theoutside. Towards the inside, it is furnished with a recess 35, in whichthe set-screw 40 is arranged, as well as bores, serving as restrictors13, between the annular groove 32 and the hollow space 16.

A cylinder bore 23 is arranged in the cylinder head wall 17 in which apiston 24 is guided which takes support on the ball race 25 and is urgedonto the ball race by a spring 21. On one side, downwardly as viewed inFIG. 2, the piston 24 is open and furnished with intake bores 29 havinga throttling effect. In the uppermost possible position of the piston24, as viewed in FIG. 2, intake bores 29 are in communication with thehollow space 16.

Spring 21 is guided by a guiding means 36 and bears against theattaching element 38. There is a connection between the interior of thepiston 24 and the pressure channel 31, in which a check valve 30 isarranged and which extends through the cylinder head wall 17 outwardly.

In operation, the pressure fluid supplied by the lubrication pressurepump 2 of the internal combustion engine into the intermediate reservoir7 propagates through the suction channel 28, composed of channel 41 andannular groove 32, to the restrictors 13 which allow passage of areduced fluid volume only. Pressure fluid is conveyed through therestrictors 13 into the hollow space 16. Rotation of the camshaft 33,through the eccentric 26 and the ball race 25, causes the piston 24 toperform upward and downward strokes. Spring 21 is rated such that itprevents the piston 24 from lifting off the ball race 25. When piston 24is in the aspirating position, which is its uppermost position as viewedin FIG. 2, pressure fluid is aspirated from the hollow space 16 throughthe intake bore 29 into the interior of the piston 24.

During the downward stroke of the piston 24, the intake bores 29 havinga throttling effect are moved away from the area of the hollow space 16and closed by the cylinder bore 23, thereby pressurizing and pumping thepressure fluid into the pressure channel 31. During the subsequentupward stroke of the piston 24, the check valve 30 prevents return flowof the pressure fluid and, thus, prevents a pressure decrease in thedirection of the consumer. As a result, vacuum develops in the interiorof the piston 24, whereby the pressure fluid prevailing in the hollowspace 16 is aspirated into the interior of the piston 24, as soon as theintake bore 29 is in communication with the hollow space 16 again.

Although illustrated and described herein with reference to certainspecific embodiments, the claims are not intended to be limited to thedetails of the specific embodiments. Rather, the claims should be readto include various modifications of the details of the specificembodiments without departing from the spirit of the invention.

List of Reference Numerals:

1 oil pan

2 lubrication pressure pump

3 filter

4 lubrication pressure line

5 supply line

6 restrictor

7 intermediate reservoir

8 overflow tank

9 hydraulic pump

10 pressure-limiting valve

11 control valve

12 operating cylinder

13 restrictor

14 return line

15 return line

16 hollow space

17 cylinder head wall

18 opening

19 consumer

20 pump element

21 spring

22 bearing

23 cylinder bore

24 piston

25 ball race

26 eccentric

27 cylinder head

28 suction channel

29 intake bore

30 check valve

31 pressure channel

32 annular groove

33 camshaft

34 cam

35 recess

36 guiding means

37 cover

38 attaching element

39 conical section

40 set-screw

41 channel

We claim:
 1. A hydraulic unit including a hydraulic pump, driven by acamshaft of an internal combustion engine, for the supply ofengine-compartment consumers in automotive vehicles, the suction side ofthe hydraulic pump being connected to an intermediate reservoir with anunrestricted overflow tank, into which operating medium from thelubrication system is supplied by the lubrication pressure pump of theinternal combustion engine, characterized in that the hydraulic pump isan externally pressurized and internally driven radial piston pumpincluding at least one pump piston and being integrated into thecylinder head of the internal combustion engine.
 2. A hydraulic unit asclaimed in claim 1, characterized in that the radial piston pump isdriven by a specially configured free end of the camshaft.
 3. Ahydraulic unit as claimed in claim 2, characterized in that the free endof the camshaft is provided with an eccentric on which a ball race isrotatably mounted, the pump piston(s) taking support on the ball race.4. A hydraulic unit as claimed in claim 3, characterized in that thecamshaft is mounted in a bearing in the cylinder head wall.
 5. Ahydraulic unit as claimed in claim 1, characterized in that the camshaftis mounted in the cylinder head, and the mounting support absorbs forceswhich are exerted on the camshaft by the hydraulic pump.
 6. A hydraulicunit as claimed in claim 5, characterized in that an opening leading tothe cylinder head is provided in the cylinder head wall, through whichthe free end of the camshaft extends, in that the opening is succeededby a hollow space accommodating the ball race and the eccentric, in thatthe cylinder head wall contains at least one cylinder bore in which eachone piston is guided, and in that the suction channel and the pressurechannel extend through the cylinder head wall.
 7. A hydraulic unit asclaimed in claim 6, characterized in that the hollow space is closed bya cover.
 8. A hydraulic unit as claimed in claim 7, characterized inthat part of the suction channel is configured in the cover, and in thatrestrictors are provided in the cover.
 9. A hydraulic unit as claimed inclaim 8, characterized in that the cover is of round shape in its fringearea, that it is furnished with a circumferential annular groove, inthat at least one bore extends from the side of the cover close to thecylinder head wall to the circumferential annular groove, and in that arecess is provided in the middle of the side of the cover close to thecylinder head.
 10. A hydraulic unit as claimed in claim 1, characterizedin that the intermediate reservoir is incorporated in the cylinder headwall.
 11. A hydraulic unit as claimed in claim 1, characterized in thatthe hydraulic pump serves for the supply of either a camshaft adjustingdevice, an automatic clutch, a differential lock, a slip control systemor a power steering system, or even a plurality of such consumers at thesame time.
 12. A hydraulic system for providing pressure fluid toconsumers in automotive vehicles, said system comprising:a lubricationsystem including a lubrication pressure pump for supplying pressurefluid; an intermediate reservoir in fluid communication with saidlubrication system for storing pressure fluid from said lubricationpressure pump; a camshaft; a cylinder head; and an externallypressurized and internally driven radial piston pump, which:(a) isdriven by said camshaft, (b) is integrated within said cylinder head,(c) has a suction side connected to said intermediate reservoir, and (d)includes at least one pump piston.
 13. A hydraulic system in accordancewith claim 12, wherein said camshaft has a free end, which is disposedradially inward relative to said at least one pump piston, for drivingsaid radial piston pump.
 14. A hydraulic system in accordance with claim13 further comprising:an eccentric coupled to said free end of saidcamshaft; and a ball race rotatably mounted on said eccentric and onwhich said at least one pump piston takes support.
 15. A hydraulicsystem in accordance with claim 14, wherein said cylinder head includesa cylinder head wall and further comprising a bearing disposed betweensaid camshaft and said cylinder head wall for mounting said camshaft insaid cylinder head wall.
 16. A hydraulic system in accordance with claim12, wherein said camshaft is mounted in said cylinder head to absorbforces which are exerted on said camshaft by said piston pump.
 17. Ahydraulic system in accordance with claim 15, wherein said cylinder headwall includes:an opening through which said camshaft extends; a hollowspace accommodating said ball race and said eccentric; at least onecylinder bore for containing said at least one piston; a suction channelfor delivering pressure fluid to said pump; and a pressure channel,radially outward relative to said at least one pump piston, throughwhich pressure fluid is conducted from said pump.
 18. A hydraulic systemin accordance with claim 17, further comprising a cover for closing saidhollow space.
 19. A hydraulic system in accordance with claim 18wherein:a portion of said suction channel is configured in said cover;and said cover is provided with restrictors.
 20. A hydraulic system inaccordance with claim 19 wherein said cover:is round in its fringe area;is furnished with a circumferential annular groove and at least one boreextending from the side of said cover close to said cylinder head wallto said circumferential annular groove; and is furnished with a recessin the middle said cover close to said cylinder head wall.
 21. Ahydraulic system in accordance with claim 18 wherein said intermediatereservoir is incorporated within said cylinder head wall.
 22. Ahydraulic system in accordance with claim 12 wherein said hydraulic pumpserves for the supply of at least one of a camshaft adjusting device, anautomatic clutch, a differential lock, a slip control system and a powersteering system.
 23. A hydraulic system in accordance with claim 12further comprising an unrestricted overflow tank in fluid communicationwith said intermediate reservoir.
 24. A hydraulic system in accordancewith claim 15 wherein said pump is disposed within the axial length saidcylinder head wall.
 25. A hydraulic system for providing pressure fluidto consumers in automotive vehicles, said system comprising:alubrication system including a lubrication pressure pump for supplyingpressure fluid; an intermediate reservoir in fluid communication withsaid lubrication system for storing pressure fluid from said lubricationpressure pump; a camshaft; and a radial piston pump, which:(a) includesat least one pump piston, (b) is internally driven by said camshaftwhich is disposed radially inward relative to said at least one pumppiston, and (c) has a suction side connected to said intermediatereservoir.
 26. A hydraulic system in accordance with claim 25 furthercomprising a cylinder head wall which defines a pressure channel,radially outward relative to said at least one pump piston, throughwhich pressure fluid is conducted from said pump.
 27. A hydraulic systemin accordance with claim 26 is wherein said pump is integrated withinsaid cylinder head wall.
 28. A hydraulic system in accordance with claim26 wherein said pump is disposed within the axial length said cylinderhead wall.